Method for real time holographic fringe blazing by determining adjacent fringe minima and blazing intermediate the minima

Abstract

Blazing of real time holographic fringes employs an interferometer with a focal plane array (FPA) to receive interference fringes. An FPA frame is read into a fringe processor. For each row, minima are identified and a pixel value is saved and its position in the row recorded. The minima determination is repeated for each column in the row until all pixels in the row have been recorded. A blazed fringe for the single row is then created. The blazed fringe row is then transferred to a spatial light modulator (SLM). The minima determination and fringe blazing processes are repeated until all rows in the FPA array are read and transferred to the SLM. The next FPA frame is then read into the fringe processor.

1. A method for blazing of real time holographic fringes comprising:
 providing an interferometer with a focal plane array (FPA) to receive interference fringes; 
 reading an FPA frame with L rows and N columns of data into a fringe processor; 
 for each row, placing an n-pixel bucket having an odd number of pixels in column data points in the row at the first column; 
 determining if a central point in the bucket is a local minima; 
 saving that pixel value and recording its position in the row; 
 shifting the bucket by one pixel; 
 repeating the step of determining if the central point in the bucket is a local minima for each column in the row until all pixels in the row have been covered by the bucket; 
 generating a blazed fringe between minima for the row; 
 transferring the row to a spatial light modulator (SLM); 
 repeating the step of determining if the central point in the bucket is a local minima for the row and the steps of generating a blazed fringe between minima and transferring the row to a spatial light modulator (SLM) until all L rows in the FPA are read; 
 reading the next FPA frame into the fringe processor. 
 
     
     
       2. The method for blazing of real time holographic fringes as defined in  claim 1  if the number of counted minima exceeds two further comprising estimating minima in an edge for applying blazing by assuming that minima adjacent the edge is repeated. 
     
     
       3. The method for blazing of real time holographic fringes as defined in  claim 1  if the number of counted minima exceeds two further comprising estimating edge minima for applying blazing by applying averaging of two minima adjacent to the edge. 
     
     
       4. The method for blazing of real time holographic fringes as defined in  claim 1  wherein the n-pixel bucket has a width of 3 pixels. 
     
     
       5. The method for blazing of real time holographic fringes as defined in  claim 1  wherein the generating of the blazed fringe is accomplished with λ/m steps per fringe where m is a number of pixels between minima and λ is a wavelength of the beam. 
     
     
       6. The method for blazing of real time holographic fringes as defined in  claim 1  wherein the step of providing an interferometer includes imbalancing aims of the interferometer such that the local minima remain above the noise floor of the FPA. 
     
     
       7. A method for combining multiple incoherent spectral optical beams comprising
 combining a plurality of incoherent spectral beams by angle using carrier frequency tilt fringes; 
 reflecting an illumination laser beam in a beam path; 
 receiving the reflected illumination beam as perturbed by the beam path; 
 forming interference fringes with the illumination beam in an interferometer having a focal plane array (FPA); 
 reading an FPA frame with L rows and N columns of data into a fringe processor; 
 for each row, placing an n-pixel bucket having an odd number of pixels in column data points in the row at the first column; 
 determining if a central point in the bucket is a local minima; 
 saving that pixel value and recording its position in the row; 
 shifting the bucket by one pixel; 
 repeating the step of determining if the central point in the bucket is a local minima for each column in the row until all pixels in the row have been covered by the bucket; 
 generating a blazed fringe for the row with λ/m steps per fringe where m is a number of pixels between minima and λ is a wavelength of the beam; 
 transferring the row to a spatial light modulator (SLM); 
 repeating the step of determining if the central point in the bucket is a local minima for the row and the steps of generating a blazed fringe between minima and transferring the row to a spatial light modulator (SLM) until all L rows in the FPA are read; 
 reading the next FPA frame into the fringe processor 
 transferring the blazed fringes to a spatial light modulator (SLM) and generating a real time hologram; 
 diffracting the combined incoherent spectral beams from the real time hologram; and 
 emitting the combined incoherent spectral beams to a far field with diffractive compensation for path perturbation. 
 
     
     
       8. The method of  claim 7  further comprising:
 segregating a portion of the reflected illumination beam as a local reference; 
 providing the local reference to the interferometer; 
 
       and wherein the step of forming interference fringes includes combining the local reference. 
     
     
       9. The method of  claim 7  wherein emitting the combined incoherent spectral beams is accomplished through relay optics and further comprising:
 transmitting the reflected illumination beam through the relay optics. 
 
     
     
       10. The method of  claim 7  wherein the step of reflecting an illumination laser beam comprises reflecting the illumination beam off a target. 
     
     
       11. The method of  claim 7  wherein the step of reflecting an illumination laser beam comprises receiving backscatter from the illumination beam. 
     
     
       12. A method for combining multiple coherent optical beams comprising:
 propagating a plurality of coherent beamlets through a collimating lens to fill an aperture with an output of combined beamlets: 
 separating a sample of the output of combined beamlets to an interferometer; 
 interfering the sample to form interference fringes on a focal plane array (FPA); 
 reading an FPA frame with L rows and N columns of data into a fringe processor; 
 for each row, placing an n-pixel bucket having an odd number of pixels in column data points in the row at the first column; 
 determining if a central point in the bucket is a local minima; 
 saving that pixel value and recording its position in the row; 
 shifting the bucket by one pixel; 
 repeating the step of determining if the central point in the bucket is a local minima for each column in the row until all pixels in the row have been covered by the bucket; 
 generating a blazed fringe for the row with λ/m steps per fringe where m is a number of pixels between minima and λ is a wavelength of the beam; 
 transferring the row to a spatial light modulator (SLM); 
 repeating the step of determining if the central point in the bucket is a local minima, for the row and the steps of generating a blazed fringe between minima and transferring the row to a spatial light modulator (SLM) until all L rows in the FPA are read; 
 transferring the blazed fringes to a spatial light modulator (SLM) and generating a real time hologram; 
 diffracting the combined beamlets transmitted by relay optics from the SLM hologram fringes; and 
 emitting the combined beamlets to the far field with diffractive compensation for tip, tilt, piston differences and wave propagation front curvatures of each sub-aperture. 
 
     
     
       13. The method of  claim 12  further comprising:
 providing a seed laser; 
 receiving an input from the seed laser for a seed beam and splitting the seed beam into multiple beanlets; 
 increasing power of the individual beamlets using a fiber amplifier array. 
 
     
     
       14. The method of  claim 13  further comprising:
 segregating one beamlet as a local reference; 
 providing the local reference to the interferometer; 
 
       and wherein the step of interfering the sample includes combining the local reference with the output of combined beamlets on a focal plane array (FPA). 
     
     
       15. The method of  claim 12  further comprising:
 demagnifying to refocus and directing the output of combined beamlets through relay optics.